small mamelonate tubercles on both ambulacral and interambulacral plates.

Range

Lower Carboniferous (Visean) to Permian, USA, Europe.

Remarks

Unfortunately, neither genus assigned to this family is particularly well known. However, the unique uniserial nature of the interambulacra distinguishes it from all others. The enclosed nature of the radial water vessel (known only for Xenechinus) suggests that the group is primitive.